LONDON — President Obama landed in London on Monday night for a state visit at a time when Britain faces a reckoning over whether it can afford the global reach its allies in Washington have come to expect.

Officials on both sides of the Atlantic are publicly hailing the strength of U.S.-U.K. bilateral ties, with Obama set to address parliament Wednesday in a speech billed as the highlight of his European trip.

Yet Obama arrives as Britain is attempting to balance financial constraints against a still ample desire for global influence — an influence bought in large part through its strategic and military alliance with the United States. Perhaps foreshadowing an election season debate in the United States about the cost of America’s own projections of power overseas, the British are wondering whether their deeply indebted nation can maintain its substantial international role.

“The British problem isn’t a lack of ambition, but to be blunt, it’s that we’ve run out of cash,” said Nick Kitchen, a professor of international affairs at the London School of Economics.

Since Britain lost its superpower status in the first half of the 20th century, its global footprint has remained remarkable for a nation its size. But bowing to fiscal pressures, Britain is already shrinking that footprint, making cuts, for instance, in the BBC World Service that once stood as a prime example of Britain’s global soft power.

More important for the U.S. alliance, British Prime Minister David Cameron is pushing for tough cuts in military spending that critics say could jeopardize Britain’s role as a long-term, frontline partner in future conflicts. The plan includes putting this nation’s lone aircraft carrier into early retirement, slashing 42,000 troops and civilian defense jobs as well as mothballing its fleet of Harrier fighter jets, a stalwart of the skies for 40 years.

The moves are set to further test the limits of British forces, which some now believe are already stretched to their limits in Afghanistan and in the NATO-led air campaign in Libya.

Earlier this month, the heads of the British Army, Royal Navy and Royal Air Force told a parliamentary committee here that in the face of the proposed cuts, Britain could no longer expect to maintain the “full spectrum” of its military capabilities. At stake is whether Britain can remain as effective a U.S. ally as it has been in the past.

The question is not just if “we have a willing accomplice in global affairs, but also a capable one,” said Nick Burns, former U.S. undersecretary of state and a professor at Harvard.

The American need for a robust British ally is felt with particular intensity in Afghanistan: Next to the United States, no ally has committed more troops — or has lost more — than Britain.

Cameron’s year-old coalition government has publicly said it wants to avoid having a “slavish” relationship with the United States, a stinging reference to Tony Blair, who as prime minister during the Iraq war years fought being labeled as President George W. Bush’s “poodle.”

But in practical terms, the relationship remains extremely close, with Cameron and Obama conferring by phone as often as twice a month. In a sign that the partnership is only deepening, the two leaders are poised to unveil a new joint “security council” this week, formally organizing high level contacts for intelligence sharing and policy coordination.

“It is not just a special relationship but an essential relationship,” Cameron said Monday in a conversation with journalists from U.S. media outlets.

Cameron praised Obama as “courageous and serious,” crediting him for the same pensive, well-considered manner that has sometimes generated criticism of the president in the United States.

Yet experts nevertheless point to disagreement between Washington and London on some key issues, most notably the desire by Britain and France to see stepped-up U.S. involvement in Libya — a topic Cameron is likely to press Obama on this week.

Meanwhile, Britain — just like the United States — has been shifting its diplomacy away from nurturing existing relationships with allies and toward improving ties with emerging economic powers like India, Brazil and Turkey. There are also differences in how Britain and the United States view China, which is seen here as less of a military and strategic threat, and more as an economic opportunity.

But the military partnership remains the core of the alliance. First and foremost in their talks this week, officials say, will be the need for Obama and Cameron to choreograph the pace of withdrawal from Afghanistan.

Cameron raised alarms in Washington by revealing plans two weeks ago for the early withdrawal of at least 400 British troops by next February — a decision apparently made public before deep consultations with his U.S. partners. The military cuts, experts say, are set to test that relationship further.

“There is considerable anxiety in Washington over the strategic implications of these sharp defense cuts, and I’m not sure the extent of that unease is fully appreciated here,” said Nigel Bowles, director of the Rothermere American Institute at Oxford University. “I would be surprised if that was not made more clear in the diplomatic exchanges this week.”

Staff writer Karen DeYoung in Washington contributed to this report.

Anthony Faiola is The Post's Berlin bureau chief. Faiola joined the Post in 1994, since then reporting for the paper from six continents and serving as bureau chief in Tokyo, Buenos Aires, New York and London.

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